Lancaster Mk II LL669 of No. 514 Squadron RAF crashed at Leiston 17 March 1944
Because of fears that R-R Merlin production would not be able to keep up with RAF orders for the new bomber. As additional insurance, B.Mk II was designed, powered by four Bristol Hercules VI or XVI radial engines. First flown in November 1941, the Mk II entered squadron service in 1942. The Hercules engined bomber was an adequate machine, but it was slower than those powered by Merlins, had a lower ceiling and carried a smaller bomb load. Production ceased after a total of 301 were built, with the type remaining in operational service until its last mission in September 1944.